Please read this sheet carefully before your appointment and bring it with you on the day. If anything is unclear, contact the Endoscopy Unit or your IBD nurse before your procedure rather than on the day.

What is a flexible sigmoidoscopy?

A flexible sigmoidoscopy is an examination of the lower part of the large bowel — the rectum, the sigmoid colon and usually the descending colon — using a thin, flexible tube with a camera at its tip, passed through the back passage. It is a shorter and gentler test than a colonoscopy: it does not examine the whole colon, it does not need full bowel preparation, and it usually takes 10 to 15 minutes. Expect to be in the department for about 2 to 3 hours. Small tissue samples (biopsies) are almost always taken; this is painless.

1 Rectum 2 Sigmoid colon 3 Descending colon 4 Splenic flexure — the usual limit of this test 5 The rest of the colon, not examined

Why is this test used in ulcerative colitis?

Ulcerative colitis almost always involves the rectum and spreads upwards, so the lower colon reliably shows how active the disease is. The test answers questions that symptoms and blood tests alone cannot: how inflamed the lining is now, whether your current treatment is working, whether the lining has healed, and — during a flare — whether an infection such as cytomegalovirus is present in the lining and making the colitis worse. It is also used at the start, to confirm the diagnosis and take the first biopsies.

What are the benefits?

Seeing the lining directly is the only way to grade inflammation objectively, and the result usually changes what happens next: continuing treatment, stepping it up, or stopping a drug that is not working. Healing of the lining is the treatment target in ulcerative colitis, not just feeling better — patients whose lining looks completely normal have about half the risk of a flare over the following year compared with those whose lining still looks mildly inflamed.

Preparing for the test

• You will usually be given one enema to use about 1 to 2 hours before you leave home, or a nurse will give it in the department. You do not need to fast or take full bowel preparation.
• If you are having a flare with frequent or bloody diarrhoea, do not use the enema. Contact the unit — the test is often done with no preparation at all in this situation, and your bowel is usually empty enough already.
• If you are admitted to hospital with a severe flare the test is done at the bedside or in the unit within the first day or two, without preparation, and is deliberately limited to the lower bowel.
• You may eat and drink normally before the test unless you are told otherwise.

Your medicines — do not stop your colitis treatment

Continue all your ulcerative colitis treatment as usual, including on the morning of the test: mesalazine, steroids, azathioprine or mercaptopurine, methotrexate, and any biologic or tablet treatment such as infliximab, vedolizumab, ustekinumab, adalimumab or a JAK inhibitor. The purpose of the test is to see how well your current treatment is working, so stopping it beforehand would make the result meaningless. Two exceptions and one caution:

• Anti-diarrhoeal medicines (loperamide, codeine): stop 3 days before, unless your doctor has told you to keep taking them.
• Iron tablets: stop 7 days before, as they stain the lining and make it harder to see.
• Blood thinners: for this test, with biopsies, these are usually continued. Contact the unit at least 7 days before so we can confirm. Do not stop them on your own.

Will I be sedated?

Sedation is not usually needed. Most patients have the test with no sedation, or with gas and air (Entonox), which wears off within about 30 minutes so you can go home alone and drive. If you choose sedation into a vein you will need a responsible adult to take you home, and for 24 hours you must not drive, operate machinery, drink alcohol or sign legal documents. Tell the team if you are anxious; the test can be paused or stopped at any point.

During the test

You will change into a gown and lie on your left side. A small amount of air or carbon dioxide is used to open the bowel, so you may feel bloating and wind, which passes. In an active flare only a little air is used and the examination is kept short. You may feel an urge to open your bowels; nothing will come out. Biopsies do not hurt.

What are the risks?

Flexible sigmoidoscopy is one of the safest endoscopic examinations — considerably safer than a colonoscopy, because it is shorter and reaches less far.

Are there alternatives?

A stool calprotectin test, blood tests and an ultrasound or MRI scan can suggest whether the colitis is active and are useful between examinations, but none shows the lining, grades the inflammation reliably or allows biopsies, so none can confirm healing or rule out infection in the lining. Choosing not to have the test is also an option; the risk is that treatment is then changed, or left unchanged, on incomplete information.

This is not the same as a surveillance colonoscopy

If your colitis affects more than the rectum you are also offered a separate colonoscopy to look for early cell changes, starting 8 years after your symptoms began and then repeated every 1, 3 or 10 years depending on your individual risk. If you also have primary sclerosing cholangitis it starts at diagnosis and is repeated every year. That test covers the whole colon, needs full bowel preparation, and is not replaced by this one.

After the test and your results

If you had no sedation you can eat, drive and return to work straight away. The findings are explained to you before you leave and a written report is given, usually including a score describing how active the inflammation looks. Biopsy results take 2 to 4 weeks and are discussed in clinic, where any change to your treatment will be decided. If you have been asked to provide a stool sample, please do so — it is a separate test from this examination and is used to check for infection during a flare.

Contact

For appointments and questions, contact the endoscopy unit using the numbers it has given you. If you are seriously unwell, or it is outside working hours, go to the Emergency Department rather than waiting for a reply.

Based on ECCO and BSG guidance on ulcerative colitis and acute severe colitis, ACG timing recommendations, BSG/ESGE antithrombotic guidance, BSG colorectal surveillance guidance and published endoscopic safety data. Supports but does not replace the discussion with your doctor and the consent process. PE-PROC-04 · Version 1.0 · October 2026 · Review due: October 2028

This leaflet is general information and does not replace advice from your own doctor.